The flow regime through eductor type debris collection devices is shown in U.S. Pat. No. 8,607,857 and US 2012/0152522. In essence the debris laden fluid is drawn into the bottom inlet pipe that has a debris collection volume around it. Other inlet and debris collection chamber configurations for such devices are also known. As the drawn debris laden fluid exits the inlet pipe the velocity is reduced due to increased cross-section and the heavier debris is redirected laterally so that it can fall into the annular shaped collection chamber around the inlet pipe. The flow continues up with some of the smaller debris that did not settle out into the annular collection chamber and passes through a screen on the way further up to an eductor inlet. The motive fluid to the eductor comes from the surface on a tubing string. The motive fluid reduces the pressure at the eductor inlet to draw the screened fluid into the eductor body and out the eductor exit. The drawn fluid mixes with the motive fluid in the eductor and the combined flow exits the device housing and can go in a downhole direction to the debris laden fluid entrance or uphole.
When using such devices one of the longstanding issues is how to alert surface personnel that there is a plugging problem and how to deal with the problem. In debris retention devices space is always at a premium and limits the practicality of some solutions to these issues. One design tries to mechanically vibrate debris off a clogged screen as illustrated in U.S. Pat. No. 8,056,622. Flow diversion schemes are discussed in U.S. Pat. No. 8,474,522 actuated with axial tool movement or pressure to move a piston. Other types of debris collection devices have sleeves shift responsive to tool movement in the hole to redirect fluid streams. One example is U.S. Pat. No. 6,607,031.
In an eductor type debris removal device a flow sensor has been proposed to sense low flow and move a sleeve over an eductor outlet port to redirect flow into the screen in a reverse direction and to give a surface signal such as with mud pulses or a pressure buildup at the surface to name a few signal options. This device proposed using a motor driven sleeve using a ball screw or thread to drive the sleeve. While using all these components could have been possible in the larger sizes, in the smaller sizes the offered design elements may not fit and the working environment is tough on sensors that require a power source in the form of a battery with a finite life.
The present invention offers a simple device responsive to loss of flow and taking advantage of the pressure reduction created by an eductor trying to draw against a clogged filter. The clogging may also be below the filter. A pressure differential across a selectively movable barrier makes that barrier move to close outlet ports on the eductor. This forces flow backwards through a screen to clean it. Further flow going backwards can also break loose a jam due to accumulated debris at the inlet to the debris removal device. The reverse flow builds pressure on the movable barrier to ultimately force the movable barrier down and have it re-latch into its original position at which time normal circulation is resumed and debris laden flow is again drawn into the bottom of the tool. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.